About 30 years ago the researchers Ziegler and Natta and others developed certain catalysts having utility for the polymerization of .alpha.-olefins. Typically these catalysts involved forming heterogeneous slurries of solutions of transition metal compounds with organometallic compound cocatalyst. Typically the organometallic cocatalyst were selected from compounds of metals of Group IA, IIA, and IIIA of the Periodic Table and the transition metal compounds were selected from compounds of the metals of Groups IIB, IVB, and VB of the Periodic Table.
Since that time second and third generation catalysts have been developed which have significantly higher activity in terms of grams of polyolefins produced per gram of catalyst than the early transition metal catalysts. In addition, the second and third generation catalysts are generally capable of providing higher isotactic index polymers when propylene or other monomers capable of giving polymers with tacticity are employed.
Many of the methods used in making the high activity catalysts and even lower activity catalysts often produce particulate catalyst compositions containing undesired levels of catalyst "fines". In most cases the presence of catalyst "fines" has resulted in polymer products which also have an undesirable level of fines. The presence of significant amounts of polymer "fines" can lead to handling problems for the catalyst or the polymer produced with it. For safety reasons and for ease of polymer processing and handling, it is therefore desirable to minimize the production of polymer fines especially those which would pass through a 200 mesh sieve.
Various techniques have been employed to produce olefin polymerization catalysts with minimal fines.
An object of the present invention is therefore to provide a novel and improved method for preparing catalyst compositions.
Another object of the present invention is to provide a novel catalyst composition well adapted for the polymerization of .alpha.-olefins. A further object of the present invention is to provide an improved process for the polymerization of .alpha.-olefins. Still another object of the present invention is to provide a process for producing .alpha.-olefin based polymers having relatively low levels of polymer fines.
These and other objects of the present invention will be apparent from the disclosure, examples, and claims provided herein.